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Title: Work function variation of MoS{sub 2} atomic layers grown with chemical vapor deposition: The effects of thickness and the adsorption of water/oxygen molecules

The electrical properties of two-dimensional atomic sheets exhibit remarkable dependences on layer thickness and surface chemistry. Here, we investigated the variation of the work function properties of MoS{sub 2} films prepared with chemical vapor deposition (CVD) on SiO{sub 2} substrates with the number of film layers. Wafer-scale CVD MoS{sub 2} films with 2, 4, and 12 layers were fabricated on SiO{sub 2}, and their properties were evaluated by using Raman and photoluminescence spectroscopies. In accordance with our X-ray photoelectron spectroscopy results, our Kelvin probe force microscopy investigation found that the surface potential of the MoS{sub 2} films increases by ∼0.15 eV when the number of layers is increased from 2 to 12. Photoemission spectroscopy (PES) with in-situ annealing under ultra high vacuum conditions was used to directly demonstrate that this work function shift is associated with the screening effects of oxygen or water molecules adsorbed on the film surface. After annealing, it was found with PES that the surface potential decreases by ∼0.2 eV upon the removal of the adsorbed layers, which confirms that adsorbed species have a role in the variation in the work function.
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4] ;  [3] ;  [5]
  1. Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Daejeon 305–701 (Korea, Republic of)
  2. (KAIST), Daejeon 305–701 (Korea, Republic of)
  3. School of Mechanical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)
  4. Beamline Research Division, Pohang Accelerator Laboratory (PAL), Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of)
  5. (SAINT) and Center for Human Interface Nano Technology (HINT), Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22483085
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 106; Journal Issue: 25; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CHEMICAL VAPOR DEPOSITION; ELECTRICAL PROPERTIES; FILMS; LAYERS; MOLYBDENUM SULFIDES; OXYGEN; PHOTOLUMINESCENCE; SILICA; SILICON OXIDES; SURFACE POTENTIAL; SURFACES; THICKNESS; WATER; WORK FUNCTIONS; X-RAY PHOTOELECTRON SPECTROSCOPY